Method and apparatus for flow control



0. O. OAKS ET AL METHOD AND APPARATUS FOR FLOW CONTROL March 12, 1935.

Filed Dec. 15, 1952 2 SheetsSheet l INVENTORS M Y B 1 m 5 5 3 3 E 5 l 9 w w 1 w 7H 8 1 TTORNEY o. 0. OAKS ET AL 1,994,047

METHOD AND APPARATUS FOR FLOW CONTROL Filed Dec.. 15. 1932 2 Sheets$neet 2 March 12, 1935.

INVENTOR O.

ATTORNEYS Patented Mai. 12, 1935 UNITED STATES PATENT OFFICE Orion 0. Oaks, Summit, N. 1., and Cesar Tex-an,

Bronxvill e, N. Y.

Application'December 15, 1932, Serial No. 647,360

29 Claims.

This invention relates to a method and apparatus for flow control in steam-circulating systems such as steamheating systems. The invention will be described in connection with a steamheating system but it is to be understood that it is not limited thereto but may be employed in connection with other steam-circulating systems.

In the venting of steam-circulating systems such as steamheating systems there are employed air valves having a port which is normally open when the system, or a radiator supplied therefrom, is cold or is not yet completely filled with steam; and the filling of the system or radiator with steam forces .air out of that port until the steam reaches the valve and causes the temperature-operated member therein to close the air port and prevent the escape of steam.

The rate at which steam will fill the system or radiator by displacing the air. therein depends upon the pressure of the steam and upon the freedom with which air flows through the valve, which freedom' of flow in turn depends generally upon the size of the air port of the air valve. If steam enters the system or radiator at a high velocity it will reach the temperature-controlled element of the air valve and cause closing of the port thereof before all of the air has been expelled from the system or radiator, and'such premature closing of the port of the air valve will cause the radiator or system to be air-bound. It is important that steam shall flow into and within the system or radiator at a low velocity in order that all of the air may be displaced therefrom before a valve of the air port is closed by the heat of the steam. Moreover, in many heating systems radiators are supplied by what is termed the one pipe system in which a single pipe leading to the radiator serves to supply the radiator with steam and at the same time carry the water of condensation from the radiator back to the main or to the boiler; and the velocity r of the steam in the pipes and entering the radiator should be low in order that such return flow of water may take place. A high velocity of steam in such a one pipe system will prevent condensed water from flowing back against 0 the movement of the steam and will eventually cause the system or the radiator or some part thereof to fill partly or completely with water.

It is generally recognizedthat variations in steam pressure are desirable, particularly in steamheating systems, in order that the resulting variations of conditions will produce what is termed a modulating effect in the system. In the operation of nearly all steamheating installations, there occur relatively wide variations of pressure normally between 0 to 5 lbs. per square inch gauge pressure, and pressures above 5 lbs. are abnormal but not unusual. In order that the higher or maximum steam pressures occurring in the operation of the system will not result in such velocity of steam flow in the system and in its parts as will cause air-binding or filling of parts of the system with water, the air port of the air-relief or air-venting valves now in use is made so small that such pressures will not produce such undesirable steam velocities in the system. However, when the steam pressure is low, e. g., substantially 0 lbs. per square inch gauge pressure, air will escape so slowly through an air port small enough to ensure proper operation at the maximum pressures occurring, that the filling of the system, with steam and particularly the filling of radiators of even average size, will-be so slow as to render the operation of the system unsatisfactory.

We have found that air-binding of the system and filling thereof with water and undesirably slow filling thereof with steam and other defects of steamheating systems are eliminated by varying the free transverse area of the vent or the resistance thereof to flow of fluid, between a normal maximum and a predetermined minimum during the flow of air therethrough, in a definite relation to variations of pressure acting upon the vent from within the system, and then completely closing the vent upon the flow of steam thereto.

It is an object of this invention to provide a method and apparatus whereby the foregoing defects in the operation of steam-circulating or steamheating systems are avoided.

In accordance with this invention the velocity of steam flowing in a steam-circulating system or flowing into a steamheating radiator is maintained at such value that air-binding and filling with water and slow filling with steam are avoided by varying the resistance of the air vent to the flow 'of fluid with variations of pressure in the system, or varying the free transverse area of the vent inversely to variations of pressure acting to cause steam to flow toward the vent and to discharge air therethrough.

In accordance with this invention the rate at which fluid passes out of the vent is maintained 5 A further feature of this invention is that the variations in the resistance to flow of fluid through the vent, or the variations in the free transverse area of the vent, are effected automatically by the pressure acting to force fluid through the vent, such variations being efiected either by the velocity of the flowing fluid or by the pressure thereof or by both such velocity and such pressure.

Further features and advantages of this invention will appear from the following description of various forms of apparatus embodying our invention and whereby our method may be practiced, such forms being described with the understanding that this invention is not limited thereto but includes all such modifications and variations as fall within the appended claims.

In the drawings in which like reference characters indicate similar parts,

Fig. 1 is a vertical sectional view of an air valve embodying certain features of our invention and whereby our method may be practiced;

Fig. 2 is an enlarged vertical section, with parts broken away, of the construction shown in Fig. 1, with the parts in a different operative position;

Figs. 3, 4 and 5 are vertical sectional views with parts broken away, of modifications of apparatus embodying further features of our invention Figs. 6 and 7 are vertical sectional views of further modifications;

Fig. 8 is a vertical sectional view, with parts broken away, of a further modification; and

Fig. 9 is a vertical sectional view, with parts broken away, of a modification similar. to the construction shown in Figs. 1 and 2.

In Fig. 1 there is shown an air vent or air valve comprising a casing 10 which is hollow and is provided with an inlet 11, which may be of any suitable construction for attachment of the valve to a steamheating or circulating system, and with passages 12, 13, 14 and 15, to the end that the valve has therethrough a passage for the flow of air from the systemto the outer atmosphere' Within the casing there is mounted in any suitable manner, as by means of spider 16, a temperature-responsive element 17 'which may be of any suitable construction and may also constitute" a float. Element 1'7 is provided with valve 18 which is adapted to close passageway or port 12 upon the flow of steam or water into casing 10. Above port 12 is located valve 19, which in the construction shown is disc-like and is provided with an upward conical extension 20, there being shown in Fig. 1 a valve seat 23 formed around port 12 and upon which valve 19 rests. Above valve 19, plug 21 having passageway 13 is so positioned in casing 10 that said passageway 13 is in axial alignment with valve 19. Upon plug 21 there is positioned, in the construction shown, a cap 22 having openings 14, to protect passage 13. When the system or radiator is cold and steam is not being supplied thereto, valve 18 is withdrawn from port 12 as shown and valve 19 seats over port 12, and valve 19 is withdrawn from passageway 13. If a low pressure forces steam into the system and toward the valve, air will enter the valve through inlet 11 and pass through port 12, slightly raising valve 20 from its seat 23, and out through passages 13 and 14. When the pressure in the system is low, passages 12, 13 and 14 are of such large diameter that flow of air therethrough and around valve 19 will permit filling of the system or radiator with steam at a rate which is sufficiently high to render satisfactory the operation of the heating system but not so high as to cause any of the objectionable occurrences above mentioned. If, however, the pressure of the steam is such as to cause it to flow within the system or radiator at such high velocity as to reach thermal unit 17 before air is thoroughly displaced from the system or radiator, or if the pressure is such as to cause steam velocities which would prevent back-flow of water, the velocity and pressure of fluid flowing through port 12 will raise valve 19 to the position shown in Fig. 2, but further venting of the system is not stopped and is only slowed down, because further flow of air will occur through passage 15 which is smaller and has more resistance to flow than has passage 13 or passage 12. Thus, passage 15 has such free transverse area and such resistance to flow of fluid that steam at the maximumpressure occurring will not cause such velocities of flow in the system as will produce the undesirable effects above mentioned. Steam pressures between the maximum and minimum will cause such velocities of steam flow that valve 19 will be raised from seat 23 a distance proportional to the velocity and vary the free flow into passage 13 inversely to the pressure. When steam reaches thermal element 17, valve 18 will seat in and close port 12, and valve 19 will assume its normal position upon its seat 23; and thereafter the valve may cool 011 to such extent that thermal element 17 withdraws valve 18 from port 12 but air will be prevented by valve 20 from entering port 12, and a vacuum will be maintained in the system and the system will be maintained filled with steam at sub-atmospheric pressures.

In Fig. 9 there is shown a modification, the operation of which is similar to that of the construction shown in Figs. 1 and 2. Thus, casing 10 is provided with a hollow boss having passageway 12 with which cooperates valve 18, and annular valve seat 23 preferably surrounds passageway 12. The open end of boss 90, is provided with a plug 91 which has an upwardly converging conical passageway 92 covered by cap 22 which is provided with openings 14. Within the chamber 93, so formed in boss 90, there is positioned a valve member 94 which may be disc-like in form and which normally rests on valve seat 23, and is provided with a guide extending into passageway 12 and with a stud 96 extending upwardly and provided with a head 9'? which is of less diameter than passageway 92. A very slight difierential of pressure under valve 94, in excess of atmospheric pressure, will raise valve 94 from its seat and permit escape of air through passageway 92; higher pressures will cause such velocity of flow in passage 12 as to cause valve 94 to rise a distance proportional to the increase of pressure with the result that head 9? is moved upwardly in passage 92 and varies inversely with the pressure the free area between head 97 and the'walls of passage 92,- thus increasing with the pressure the resistance to flow of fluid through passage 12; and pressures .great enough to-cause steam flow velocities which are rapid enough to impair the operation of the system, will raise which varies the free venting area acts to close the passage through the valve against return flow of air at all times when the pressure within the system is sub-atmospheric.

Referring to Fig. 3, there is positioned above port 12 a housing 24 which has an outlet opening 25 and across which there extends a dia-. phragm 26 supported in any suitable manner, as

I by making the upper portion 27 of housing 24 separate from the lower portion thereof and threading the two portions together with the periphery of the diaphram clamped between them as shown in the drawings. It is to be noted that these details of construction are only illustrative and that the invention is not limited thereto, it being noted in this connection that a collapsible element or bellows may be employed in lieu of a diaphram in this and othermodifications described as containing a diaphram. In housing 24 there are adjustably supported, as by being mounted upon stud 28, two valve members 30 and 31. A cooperating valve member 32 is carried by diaphram 26 and is provided with a passage 33 which fixes the minimum free passage through the valve existing when valve 18 is open. The sensitivity of diaphram 26 is adiusted by spring 80 which surrounds valve member 32 and has one of its ends in engagement with diaphram 26 and the other of its ends in engagement with flange 81 of sleeve 82 and is more or less compressed by adjustment of sleeve 82 which is threaded in housing'24 and locked in place by 1001; nut 83. Stud 28 is threaded in sleeve 82 and fixed by lock nut29. When a low pressure is forcing air towardthe valve it will act on diaphram 26 and the lower end of valve member 32 will'be lifted from valve 31 and the' free transverse area of the passageway through valve member 32 will permit rapid venting of air but not such rapidventing as will cause steam velocities which result in defective operation above-mentioned; higher pressures will proportionately raise diaphram 26- and valve member 32 and vary the free area between valve members 30 and 32 inversely to the pressure; and pressuresof steam-high enough to cause such objectionable operation will cause diaphram 26 to raise valve member 32 until its upper end engages valve member 30 and limits the free passage through the valve to the relatively small transverse area of passage 33. After valve 18 is closed the pressure on the lower side of diaphram 26 is dissipated; and the lower end of valve member 32 will seat upon valve member 31 and prevent flow of air into the system when valve 18 again opens, thereby preserving a vacuum in the system. Y

Referring to Fig. 4, the upper part of port 12 is provided with a ball or other type of check valve 34 which preserves a vacuum in the system, and above port 12 is located housing 24 containing diaphram 126, but in this construction .diaphram 126 carries a valve member which cooperates with other valve members to produce a balanced valve. Thus, there extends into the side of housing 24 a hollow member 35 which'is open to the atmosphere and carried valve seats 36 and 3'! with which respectively cooperate valves 38 and 39 carried on spindle 40 which is attached to diaphram 126. The sensitivity of diaphram 126 is adjusted by spring 41 which bears thereupon and is more or less compressed by adjustment of screw plug 42. Normally valves 38 and 39 are spaced from seats 36 and 37 providing a relatively large free passage through the valve; and increase of pressure on diaphram 126 will inversely vary the area of that passage. Through the wall of hollow member 35 leads passageway 43 which provides the minimum free opening when valves 37 and 38 are completely closed by the action of such pressure on diaphram 126 as would cause undesirable steam velocities in the system.

In Fig. 5 there is provided above port 12 the housing 24 carrying diaphragm 26 and having outlet 25. Within housing 24 and above port 12 there is positioned valve 44 which is similar in form and operation to valve 19 shown in Fig. 1, and in alignment'therewith diaphragm 26 carries a valve member 45 and also in alignment with valve members 44 and45 there is positioned valve member 46. Valve member 45 is provided with an opening 47 below diaphragm 26 and a smaller opening 48 above diaphragm 26. Valve member 46 is slidably mounted on stud 49 and prevented from sliding off of that stud by collar 50. Spring 51 presses valve member 46 normally against collar 50 and it is mounted upon plug 52 threaded into the top of housing 44 in order that the tension of spring 51 may be adjusted, stud 49 being threaded into plug 52 and locked by nut 53 in order that the position of valve 46 and the tension of spring 51 may be independently adjusted. When the steam pressure is low the air is vented at such a rate as will not cause undesirable steam velocities but will cause sufficiently rapid filling of the system or radiator with steam, by raising valve 44 and flowing between valves 44 and 45 and inwardly through opening 47 and between valves 45 and 46 and outwardly through opening 48. Higher pressures which might cause undesirable steam velocities in the system if vented through such large passages act upon valve 44 and lift it into engagement with valve member 45, and the venting is through larger passage 4'! and through the space between valve members 45 and 46 and through smaller passage 48. Further increases of pressure cause diaphram 26 to lift valve member 45 into engagement with valve member 46 and the venting is limited by the relatively small free transverse area of opening 48. In the valve member 45 causes the lower end of stud 49 to engage and unseat valve 44 from the lower end of valve member 45. Valve member 44 acts as a check valve to preserve vacuum in the system. The downward deflection of diaphragm 26 is limited by engagement of annular plate 84 carried thereby with posts 85 threaded casing 10 a partition 54 having a passage 55- with which cooperates valve 56 and having als-., a small opening 57 which providesthe minimum construction shown in Fig. 5, further rising of partition 64 in any suitable manner, as by conduit 61. When low pressures exist venting occurs through relatively large port 12, lifting 'check valve 34 whichlater seals the system to preserve vacuum. Pressures which would cause such rapid venting through large port 12 as to give undesirable velocities in the system will depress diaphram 58 and move valve 56 more or less toward or against partition 54 and partly or completely close passage 55, port 57 being unaffected by the position of valve 56. When action of steam closes valve 18 passage 61 allows equalization of pressure on both sides of diaphram 58 thereby allowing valve 56 to open.

The construction in Fig. 7 is similar to that shown in Fig. 6 except that a balanced valve is provided by mounting on partition 154 a hollow member 63 communicating with the space above partition 154 and carrying valve members 64 and 65 with which respectively cooperate valve members 66 and 67 carried by diaphram 58. Hollow member 63 is provided with minimum vent passage 68.

The construction shown in Fig. 8 is somewhat similar to that shown in Fig. 4 except that the pressure acts on the opposite side of the balanced valve. Thus, within housing 24 and leading-upward from port 12 thereis a hollow member 69 carrying valve members 70 and 71 which cooperate respectively with valve members '72 and 73 carried by diaphram 26 on stud 40. Hollow member 69 is provided with a minii'num vent passage 74. Leading from housing 24 is a vent pipe 125. Pressures so low that they will not cause undesirable velocities of steam in the system cause air to pass through port'12, raise check valve 34, and pass between valve members 70 and 72 upon the one hand and '71 and 73 on the other hand and through minimum opening '14 and out through pipe 125. Higher pressures causing more rapid flow of air will cause increase of resistance to flow in the relatively long pipe 125 and the resulting back-pressure will lift diaphram 26 and cause valve members 72 and '73 to move toward or against valve members '70 and '71, thus increasing the resistance to flow of fluid through the valve and decreasing the free transverse area of the free passage through the casing.

A feature of this invention is that the principles thereof apply to the control of the flow of fluid at any point of a steam-distributing system. Thus, the means embodying this invention and varying the resistance to flow with the pressure or velocity, or both, of the flowing fluid, may be located in the system between any portion thereof, such as between a radiator and the thermostaticallyor float-controlled terminal outlet 12; and similarly said means may be located at the inlet of any branch of the system, such as at a radiator inlet, or at any other intermediate point of the system. Accordingly the passage through a flow control valve embodying this invention may be put into communication with a steam-distributing system by connecting the valve to the system at a terminal thereof, or connecting it into the system at a branch thereof,'or connecting it into the system in series at any point thereof.

Obviously, a reference herein to parallel branches of a passage is intended only to indicate that those passages are parallel functionally and is not intended as a limitation to any particular geometrical relation of the branches.

We claim:

1.- In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, and means for increasing the resistance to the flow of fluid through said passage with increase of pressure in the system.

2. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, a thermostaticallyoperated valve for opening and closing said passage, and means for decreasing while said passage is open the free transverse area of said passage with increase of pressure in the system.

3. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, and means responsive to the velocity of fluid flowing through said passage for increasing the resistance to the flow of fluid through said passage with increase of pressure in the system.

4. In a flow-control valve for a; steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, a thermostatically-operated valve for opening and closing said passage, and means actuated by flow of fluid in said passage for varying while said passage is open the free transverse area of said passage inversely to variations of pressure in the system.

5. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, and means for varying the free transverse area of the passage, between a normal maximum and a predetermined minimum adapted to permit continued flow of fluid through said passage, inversely to variations of pressure in the system.

6. In an air-relief valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, a temperatureoperated valve for opening and closing said passage, and means operative while said valve is open for maintaining substantially constant the rate of flow of fluid flowing through said passage under the influence of different pressures in the system.

'7. In a flow-control valve fora steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, means dividing said passage at a point between its ends into a plurality of parallel branches, and valve means for closing one of said branches while leaving an other of said branches open when the pressure in the system exceeds a predetermined value.

8. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, means dividing said passage at a point between its ends into a plurality of parallel branches, and a valve memtit her movable between a position closing said passage against flow of atmospheric air therethrough to said system and a position closing one of said branches against flow of fluid from said casing to the atmospheric air.

9. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, opposed valve seats in said casing, a thermostatically operated value for opening and closing said passage, and a valve member having a tapering portion adapted to extend into one of said valve seats to vary inversely to the pressure in the system the flow of fluid in said passage in one direction and having a portion adapted to engage the other of said seats to close said passage against flow in the opposite direction.

10. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, means dividing said passage at a point between its ends into a plurality of parallel branches, and a valve member movable to vary flow in one of said branches in one direction and to close said passage against flow in the opposite direction.

11. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, means dividing said passage at a point between its ends into a plurality of parallel branches, a valve seat for said passage, a valve seat for one of said branches, and a valve member movable to position in which it respectively engages said seats.

12. In a flow-control valve for a steam-distributing system, a casing having a passagebeing adapted to close said passage against flow in the opposite direction.

13. In the control of flow of fluid in a conduit, the steps comprising dividing the stream of fluid into a plurality of parallel streams at one point thereof, varying with the pressure tending to produce flow of fluid in the stream the resistance to the flow of fluid ofTJne of said branches in one direction, and blocking the flow of fluid of said stream in the opposite direction.

14. In the air-venting of a steam heating system, the steps comprising flowing a stream of fluid from the system, dividing said stream into a plurality of branches, varying the resistance to flow of one of said branches with the pressure tending to produce flow of the stream, and thermostatically controlling the flow of the stream.

15. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, a thermostatically operated valve for opening and closing said passage, and means for varying while said valve is open the free transverse area of the passage, between a normal maximum and a predetermined minimum adapted to permit continued flow of fluid through said passage, inversely to variations of pressure in the system.

16. In a flow-control valve for a steam-distributing system, a casing having a passage therethrough which is adapted to be put into communication with the system, and a valve member movable to vary but not completely stop the "flow through said passage in one direction and to close said passage against flow in the opposite direction.

17. In the air-venting of a steam-heating system, the steps comprising flowing a stream of fluid from the system; varying the transverse area of the stream, between a normal maximum and a predetermined minimum that permits continued flow of the stream, inversely to the pressure tending to produce flow of the stream; and thermostatically efiecting a complete obstruction of the stream.

18. In the air-venting of a steam-heating system, the steps comprising flowing a stream of fluid from the system; varying the resistance to the flow of the stream, between a normal minimum and a predetermined maximum that permits continued flow of the stream, with the pressure tending to produce flow of the stream; and thermostatically effecting a complete obstruction of the stream.

19. In a flow control valve for a steam distributing system, a casing adapted to be put in communication with said system, a, vent for said casing, a thermostatically operated valve for closing said vent, and means responsive'to the velocity of fluid flow through said vent for decreasing the efiective area thereof with increase of pressure in the system.

20. In a flow control valve for a steam distributing system, a casing adapted to be put in communication with said system, a vent for said casing, a thermostatically operated valve for closing said vent, argd means responsive to the velocity of fluid flow through said vent for maintaining substantially constant the rate of fluid flow through said vent under the influence of different pressures in the system.

22. In a flow control valve for a steam distributing system, a casing adapted to be put in communication with said system, a vent for said casing, said vent having parallel branches and a valve responsive to the velocity of fluid flow through said vent for closing one of said branches while leaving the other of said branches open when the pressure in the system exceeds a predetermined value.

23. In a flow control valve for a steam distributing system, a casingadapted to be put in communication with said system, a vent for said casing, a thermostatically operated valve for closing said vent, and means responsive to the velocity of fluid flow through said' vent for decreasing the effective area of said ,vent with increase of pressure in the system from a normal maximum to a predetermined minimum.

24. In a flow control valve for a steam distributing system, a casing adapted to be put in communication with said system, a vent for said casing, a thermostatically operated valve for closing said vent, and a valve member effective to prevent inward fluid flow through said vent and responsive to variations of fluid flow out-.

wardly through said vent for decreasing the efiective area thereof with pressure increase in the system.

25. In a flow control valve for a stream distributing system, a casing to be put in communication with said system, a vent for said casing, a thermostatically operated valve for closing said vent, said vent having parallel branches and a valve member effective to prevent inward flow through said vent and responsive to variations of fluid flow outwardly through said vent for closing one of said branches while leaving the other of said branches open upon increase of pressure in said system.

26. In a flow control valve for a steam dis tributing system, a casing adapted to be put in communication with said system, a vent for said casing, valve means responsive to variations of fluid flow outwardly through said vent for decreasing the effective area thereof with pressure increase in the system, and valve means non-responsive to temperature variations for preventing inward fluid flow through said vent.

27. In a flow control valve for a steam distributing system, a casing adapted to be put in communication with said system, a vent for said casing, and valve means non-responsive to temperature variation for preventing inward flow through said vent, said valve means being responsive to variations of fluid flow outwardly through said vent for decreasing the effective area thereof with pressure increase in the system.

28. In a flow control valve for a steam distributing system, a casing adapted to be put into communication with said system, a vent for said casing, said vent having parallel branches and a valve member movable axially with respect to one of said branches, the opposed surfaces of said branch and said valve member having a relative taper in the direction of movement of said valve member, whereby flow through said branch is varied by movement of said valve member, said valve member being responsive to variations of fluid flow outwardly through said vent for closing said branch with increase of pressure in the system 29. In a flow control valve for a steam distributing system, a casing adapted to be put in communication with the system, a vent for said casing, opposed valve seats in said vent and a valve member adapted to engage either of said seats, the opposed surfaces of one seat and said valve member having a relative taper in the direction of movement of said valve member, whereby outward flow through said vent is varied and said valve member being adapted to close said vent against inward flow.

ORION O. OAKS.

CESAR TERAN. 

